I watched a serial that narrates how Shiva created Vishnu and Brahma to create and save Earth and all the souls. I have not read this in any of the scriptures but could someone point me to the source of this story?
Yes, there are plenty of scriptures which tell Lord Shiva created Lord Brahma and Lord Vishnu just as there are scriptures which say Lord Vishnu created Lord Brahma and Lord Rudra or Lord Brahma took form as Lord Vishnu or Lord Rudra (some verses which I discuss in my answer here.)
The main place to see for these things would be Puranas which are primarily focussed to Lord Shiva, like the Shiva Purana, Linga Purana and Vayu Purana etc...
The answer discussed here quotes from Shiva Purana:
Shiva thought within Himself like this-" Another being shall be created by me. Let him create everything, protect it and in the end dissolve it. The supreme lord , Shiva , spread liquorice essence of nectar on His left side, on tenth limb, nectar which was the outcome of churning the ocean of His mind wherein thoughts were the waves, Satva Guna was the precious Gem, Rajas being coral and Tama being crocodile. Thereupon a person came into being who was most charming one in the three worlds, who was calm with sattva guna prominent, and appeared to be ocean of immeasurable majesty. Siva said to him-" You will be famous as VISHNU by name as you all pervasive. You will have many other names conferring happiness on devotees. Perform penance highly conducive to achievement of matter in hand. Be firm on it". Saying so lord bestowed Vedas on him through nostrils.
Similarly plenty of similar verses are also found in Linga Purana and Vayu Purana. Even in the Puranas which are not specifically related to Lord Shiva, we may find such verses. For instance like in Padma Purana which I discuss here:
य एकः शाश्वतोदेवोब्रह्मवंद्यः सदाशिवः ।
त्रिलोचनो गुणाधारोगुणातीतोऽक्षरोव्ययः ।।
जातमात्रास्त्रयोदेवाब्रह्मविष्णुमहेश्वराः।। (Padma Purana Patala Khanda chapter 108)
He who is that eternal god SadaShiva,who is saluted by Brahma, who has three eyes, who is the prop of virtues, who is beyond qualities, who is unchangeable and immutable. O dear one, having divided himself and the region there, he created on his right side the son, viz. Brahma and Hari from his left side. At the back side he created Mahesh; thus the mighty one created three sons. As soon as they were born they became the three gods—Brahma, Vishnu and Maheswara.
Similarly in various places of Mahabharata too, like in this chapter:
स एष भगवान्देवः सर्वतत्त्वादिरव्ययः।
वामपार्श्वात्तथा विष्णुं लोकरक्षार्थमीश्वरः।।
युगान्ते चैव संप्राप्ते रुद्रमङ्गात्सृजत्प्रभुः।
स रुद्रः संहरन्कृत्स्नं जगत्स्थावरजङ्गमम्।।
कालो भूत्वा महातेजाः संवर्तक इवानलः।
एष देवो महादेवो जगत्सृष्ट्वा चराचरम्।।
कल्पान्ते चैव सर्वेषां स्मृतिमाक्षिप्य तिष्ठति।
सर्वगः सर्वभूतात्मा सर्वभूतभवोद्भवः।।
आस्ते सर्वगतो नित्यमदृश्यः सर्वदैवतैः।
O puissant and illustrious one, thee that art the beginning of all the topics, thee that art indestructible and changeless, thee that art conversant with the ordinances which govern all the topics, thee that art the foremost of Purushas, thee that art the highest of the high. Thou art he that hadst created from thy right side the Grandsire Brahma, the Creator of all things. Thou art he that hadst created from thy left side Vishnu for protecting the Creation. Thou art that puissant Lord who didst create Rudra when the end of the Yuga came and when the Creation was once more to be dissolved. That Rudra, who sprang from thee destroyed the Creation with all its mobile and immobile beings, assuming the form of Kāla of great energy, of the cloud Samvartaka (charged with water which myriads of oceans are not capacious enough to bear), and of the all consuming fire. Verily, when the period comes for the dissolution of the universe, that Rudra stands, ready to swallow up the universe. Thou art that Mahadeva, who is the original Creator of the universe with all its mobile and immobile entities. Thou art he, who, at the end of the Kalpa, stands, withdrawing all things into thyself. Thou art he that pervadest all things, that art the Soul of all things, thou art the Creator of the Creator of all entities.